1. Field of the Invention
This invention relates to an apparatus for adjusting the rigidity of vehicle body that controls the rigidity of a frame and the like of a vehicle body so as to appropriately absorb collision energy in accordance with a collision form and a colliding subject.
Priority is claimed on Japanese Patent Application Nos. 2004-157694, filed May 27, 2004, and 2005-112479, filed Apr. 8, 2005, the contents of which are incorporated herein by reference.
2. Description of Related Art
There is a conventional apparatus for adjusting the rigidity of vehicle body that controls the rigidity of the vehicle body by using piezoelectric actuators, which are placed on side frames attached to left and right sides of the vehicle, to apply a force that resists or promotes a collision load received from the front of the vehicle to the side frames, thereby switching the rigidity of the side frames in order to deal with different forms of collision (e.g. see Japanese Unexamined Patent Application, First Publication, No. H11-291951). Specifically, the structure of this apparatus reduces the rigidity of the side frames in a full lap collision against the entire front face of the vehicle body, and increases the rigidity of the side frame in an offset collision where the collision load is focused on one side frame.
Another conventional apparatus determines whether there is a collision based on, for example, results detected by acceleration sensors and the like, and, when there is a collision, expedites deformation of a front bumper beam, reducing the rigidity of the front bumper beam by allowing part of it to break (e.g. see Published Japanese Translation No. 2001-504413 of the PCT International Publication).
However, the above-described conventional apparatus for adjusting the rigidity of vehicle body requires a large amount of electric power to actuate the piezoelectric actuators, due to the generation in the piezoelectric actuators of the force that resists the collision load (i.e. the force that directly receives the collision load). A disadvantage of this is that the piezoelectric actuators themselves become larger, as does a battery that supplies power to them.
The conventional apparatus that allows part of the beam to break merely reduces the rigidity of the beam to a predetermined level whenever there is a collision, and cannot appropriately modify its rigidity in accordance with the level of the collision and the subject that it collides with.